The opening/closing lifetime of the circuit breaker includes a mechanical one and an electrical one. The former depends chiefly on wear and damage of its mechanical component. Meanwhile, the latter is dominated by, in addition to those, wear and tear of contacts, normally being shorter in lifetime than the former. Regarding the damage of the mechanical component, a fatigue burnout of parts that perform electrical connections by means of a flat stranded copper wire or a sheet metal that provides flexibility (hereinafter referred to as shunt), is particularly a major cause that limits the opening/closing lifetime.
As a measure for eliminating the cause, a current-carrying mechanism is known that increases a contact pressure between a movable contact and a movable contact arm support, by slidably contacting the movable contact with the movable contact arm support, and using a compression spring placed outside the movable contact arm. The electrical contact between the movable contact and the movable contact arm support is generally referred to as “shuntless current-carrying mechanism” because the fore-mentioned shunt is not to be employed. e.g., refer to Patent Documents 1 and 2.
Patent Document 1    Japan Patent Publication H09-306326
Patent Document 2    Japan Patent Publication H07-006681